Microscopic Research on the Olfactory Organ of the Blue Spotted Mudskipper Boleophthalmus pectinirostris, Compared to a Related Sympatric Mudskipper

Anatomical, histological, and histochemical investigations on the olfactory organ of the great blue spotted mudskipper Boleophthalmus pectinirostris were conducted using a stereo microscope, light microscope, scanning electron microscope, and transmission electron microscope. Analysis showed that B. pectinirostris has 1) a downward tubular anterior nostril, 2) slit posterior nostril, 3) ethmoidal and lacrimal accessory nasal sacs, 4) a continuous type of SE distribution, 5) olfactory receptor neuron cilia three to four times longer than the diameter of the knob, 6) a surface of supporting cells with long cilia, 7) a specific-histochemistry of mucous cell, and 8) cylindrical and large ion-exchanging cells with numerous mitochondria. Among these characteristics, some (3∼8) show clear differences in comparison to the sympatric mudskipper, Periophthalmus modestus. Such differences of the olfactory organ may reflect adaptive responses to aerial exposure and microhabitat for amphibious life. Also, the olfactory organ is considered a morphological differentiating characteristic, at least in the subfamily Oxudercinae.